Three-dimensional image retrieving techniques are important for many applications. These techniques can roughly be divided into interferometric and non-interferometric techniques. Digital Holographic Microscopy (DHM) is an interferometric non-invasive technique for acquiring real-time quantitative phase images which has an enormous impact in many fields such as biology of living cells, neural science, nanoparticle tracking, biophotonics, bioengineering and biological processes, microfluidics, and metrology. A DHM system records a digital hologram optically using a microscope objective (MO) and the image reconstruction is performed digitally using optical propagation techniques, see, G. Nehmetallah, R. Aylo and L. Williams, Analog and Digital Holography with MATLAB®, SPIE Press, Bellingham, Wash., 2015, incorporated herein by reference in its entirety.
However, the use of an MO introduces phase aberrations which can be superposed over the biological sample (object). A successful image reconstruction requires very tedious alignment and precise measurement of the system parameters such as reference beam angle, reconstruction distance, and MO's focal length which are often difficult to achieve in a laboratory environment. To overcome these difficulties, the use of multiple-wavelength DHM and telecentric DHM configurations were employed which allowed canceling the bulk of optical phase aberration due to the MO and the reference beam. Residual aberrations could be compensated digitally by using Principal Components Analysis (PCA) or Zernike polynomial fitting (ZPF). However, as recognized by the present inventors, the use of multi-wavelength source makes the system setup more complicated and expensive. In addition, the existing digital compensation techniques still have other drawbacks, as recognized by the present inventors. The ZPF requires background information to find the phase residual which is detected semi-manually by cropping background area to perform the fitting. PCA, on the other hand, automatically predicts phase residual by creating a self-conjugated phase to compensate for the aberrations but assuming that the phase aberrations have only linear and spherical components and leaving higher order phase aberrations unaccounted for. Therefore, an automatic detection of the background areas in DHM would be highly desired. Many segmentation techniques have been proposed which can be divided into semi-automatic techniques such as active contour, region growing, graph cut, and random walker, which require predefined seeds, and fully automatic segmentation techniques such as edge-based, region-based, split and merge, and watershed techniques. However, in the case of DHM, these existing methods are not reliable because of the overwhelming phase aberrations and speckle noise in the images.
The foregoing “Background” description is for the purpose of generally presenting the context of the disclosure. Work of the inventor, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention. The foregoing paragraphs have been provided by way of general introduction, and are not intended to limit the scope of the following claims. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.